## BC BREAK: the PDO symbols are no longer part of the DBAL API
1. The support of `PDO::PARAM_*`, `PDO::FETCH_*`, `PDO::CASE_*` and `PDO::PARAM_INPUT_OUTPUT` constants in the DBAL API is removed.
2.`\Doctrine\DBAL\Driver\PDOStatement` does not extend `\PDOStatement` anymore.
2.`\Doctrine\DBAL\Driver\PDOConnection` does not extend `\PDO` anymore. Please use `\Doctrine\DBAL\Driver\PDOConnection::getWrappedConnection()` to access the underlying `PDO` object.
3.`\Doctrine\DBAL\Driver\PDOStatement` does not extend `\PDOStatement` anymore.
